drm/xe: Pass a drm_pagemap pointer around with the memory advise attributes

As a consequence, struct xe_vma_mem_attr() can't simply be assigned
or freed without taking the reference count of individual members
into account. Also add helpers to do that.

v2:
- Move some calls to xe_vma_mem_attr_fini() to xe_vma_free(). (Matt Brost)
v3:
- Rebase.

Signed-off-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com> #v2
Link: https://patch.msgid.link/20251219113320.183860-13-thomas.hellstrom@linux.intel.com

drivers/gpu/drm/xe/xe_svm.c

@@ -290,10 +290,14 @@ static int __xe_svm_garbage_collector(struct xe_vm *vm,
 
 static void xe_vma_set_default_attributes(struct xe_vma *vma)
 {
-	vma->attr.preferred_loc.devmem_fd = DRM_XE_PREFERRED_LOC_DEFAULT_DEVICE;
-	vma->attr.preferred_loc.migration_policy = DRM_XE_MIGRATE_ALL_PAGES;
-	vma->attr.pat_index = vma->attr.default_pat_index;
-	vma->attr.atomic_access = DRM_XE_ATOMIC_UNDEFINED;
+	struct xe_vma_mem_attr default_attr = {
+		.preferred_loc.devmem_fd = DRM_XE_PREFERRED_LOC_DEFAULT_DEVICE,
+		.preferred_loc.migration_policy = DRM_XE_MIGRATE_ALL_PAGES,
+		.pat_index = vma->attr.default_pat_index,
+		.atomic_access = DRM_XE_ATOMIC_UNDEFINED,
+	};
+
+	xe_vma_mem_attr_copy(&vma->attr, &default_attr);
 }
 
 static int xe_svm_range_set_default_attr(struct xe_vm *vm, u64 start, u64 end)

drivers/gpu/drm/xe/xe_vm.c

@@ -957,14 +957,37 @@ struct dma_fence *xe_vm_range_unbind(struct xe_vm *vm,
 	return fence;
 }
 
+static void xe_vma_mem_attr_fini(struct xe_vma_mem_attr *attr)
+{
+	drm_pagemap_put(attr->preferred_loc.dpagemap);
+}
+
 static void xe_vma_free(struct xe_vma *vma)
 {
+	xe_vma_mem_attr_fini(&vma->attr);
+
 	if (xe_vma_is_userptr(vma))
 		kfree(to_userptr_vma(vma));
 	else
 		kfree(vma);
 }
 
+/**
+ * xe_vma_mem_attr_copy() - copy an xe_vma_mem_attr structure.
+ * @to: Destination.
+ * @from: Source.
+ *
+ * Copies an xe_vma_mem_attr structure taking care to get reference
+ * counting of individual members right.
+ */
+void xe_vma_mem_attr_copy(struct xe_vma_mem_attr *to, struct xe_vma_mem_attr *from)
+{
+	xe_vma_mem_attr_fini(to);
+	*to = *from;
+	if (to->preferred_loc.dpagemap)
+		drm_pagemap_get(to->preferred_loc.dpagemap);
+}
+
 static struct xe_vma *xe_vma_create(struct xe_vm *vm,
 				    struct xe_bo *bo,
 				    u64 bo_offset_or_userptr,
@@ -1015,8 +1038,7 @@ static struct xe_vma *xe_vma_create(struct xe_vm *vm,
 	if (vm->xe->info.has_atomic_enable_pte_bit)
 		vma->gpuva.flags |= XE_VMA_ATOMIC_PTE_BIT;
 
-	vma->attr = *attr;
-
+	xe_vma_mem_attr_copy(&vma->attr, attr);
 	if (bo) {
 		struct drm_gpuvm_bo *vm_bo;
 
@@ -4324,7 +4346,7 @@ static int xe_vm_alloc_vma(struct xe_vm *vm,
 	struct drm_gpuva_op *__op;
 	unsigned int vma_flags = 0;
 	bool remap_op = false;
-	struct xe_vma_mem_attr tmp_attr;
+	struct xe_vma_mem_attr tmp_attr = {};
 	u16 default_pat;
 	int err;
 
@@ -4419,7 +4441,7 @@ static int xe_vm_alloc_vma(struct xe_vm *vm,
 			 * VMA, so they can be assigned to newly MAP created vma.
 			 */
 			if (is_madvise)
-				tmp_attr = vma->attr;
+				xe_vma_mem_attr_copy(&tmp_attr, &vma->attr);
 
 			xe_vma_destroy(gpuva_to_vma(op->base.remap.unmap->va), NULL);
 		} else if (__op->op == DRM_GPUVA_OP_MAP) {
@@ -4429,12 +4451,13 @@ static int xe_vm_alloc_vma(struct xe_vm *vm,
 			 * copy them to new vma.
 			 */
 			if (is_madvise)
-				vma->attr = tmp_attr;
+				xe_vma_mem_attr_copy(&vma->attr, &tmp_attr);
 		}
 	}
 
 	xe_vm_unlock(vm);
 	drm_gpuva_ops_free(&vm->gpuvm, ops);
+	xe_vma_mem_attr_fini(&tmp_attr);
 	return 0;
 
 unwind_ops:
@@ -4532,3 +4555,4 @@ int xe_vm_alloc_cpu_addr_mirror_vma(struct xe_vm *vm, uint64_t start, uint64_t r
 
 	return xe_vm_alloc_vma(vm, &map_req, false);
 }
+

drivers/gpu/drm/xe/xe_vm.h

@@ -414,4 +414,5 @@ static inline struct drm_exec *xe_vm_validation_exec(struct xe_vm *vm)
 #define xe_vm_has_valid_gpu_mapping(tile, tile_present, tile_invalidated)	\
 	((READ_ONCE(tile_present) & ~READ_ONCE(tile_invalidated)) & BIT((tile)->id))
 
+void xe_vma_mem_attr_copy(struct xe_vma_mem_attr *to, struct xe_vma_mem_attr *from);
 #endif

drivers/gpu/drm/xe/xe_vm_madvise.c

@@ -95,6 +95,7 @@ static void madvise_preferred_mem_loc(struct xe_device *xe, struct xe_vm *vm,
 			 */
 			vmas[i]->attr.preferred_loc.migration_policy =
 						op->preferred_mem_loc.migration_policy;
+			vmas[i]->attr.preferred_loc.dpagemap = NULL;
 		}
 	}
 }

drivers/gpu/drm/xe/xe_vm_types.h

@@ -20,6 +20,8 @@
 #include "xe_range_fence.h"
 #include "xe_userptr.h"
 
+struct drm_pagemap;
+
 struct xe_bo;
 struct xe_svm_range;
 struct xe_sync_entry;
@@ -65,6 +67,13 @@ struct xe_vma_mem_attr {
 		 * closest device memory respectively.
 		 */
 		u32 devmem_fd;
+		/**
+		 * @preferred_loc.dpagemap: Reference-counted pointer to the drm_pagemap preferred
+		 * for migration on a SVM page-fault. The pointer is protected by the
+		 * vm lock, and is %NULL if @devmem_fd should be consulted for special
+		 * values.
+		 */
+		struct drm_pagemap *dpagemap;
 	} preferred_loc;
 
 	/**